The present invention relates to a transparent face shield, in particular for heat protection clothing, such as protective suits or protective hoods, with a pane made of polycarbonate coated on the outside with gold by vapor deposition.
In the construction of heat protection clothing the basic problem lies in the provision of face shields which are, on the one hand, fully transparent and, on the other hand, have a high degree of heat resistance.
Glass or plastic can be considered as basic materials for this, each of which has specific advantages and disadvantages: Use of glass, particularly in the form of a laminated glass pane, as a face shield has the advantage of a very high degree of heat resistance However, it is breakable, very heavy and can be provided only in small sizes (approximately 250.times.150 mm) because of considerable manufacturing restrictions, so that only a restricted field of vision is possible, which impedes use to a considerable extent.
Plastic has been used for a known face shield in the form of a polycarbonate with a gold coating layer deposited on the outside by vapor deposition, where the gold layer serves as a reflecting layer for radiant heat and in this way can reduce the temperature of the polycarbonate behind it.
But since polycarbonate has a comparatively low melting point and since damage to the deposited gold layer continues to occur in practical use, the softening tendency of the shield has made such face shield totally useless.
The advantages of plastic, such as low weight and ease of molding into appropriate shapes thus must be paid for by only limited safety in use, caused by the loss of mechanical stability.